Physical Properties of $LiPF_6/PC+EC+DEC$ Electrolyte by the Variation of PC Fraction and Initial Electrochemical Properties of Carbon Anode in the Electrolyte

Abstract

The exfoliation of graphite (layer) was progressed due to the irreversible insertion of PC molecules between graphene layers, when propylene carbonate (PC) solvent was used as the organic solvents. The problem could be mitigated by the replacement of PC by ethylene carbonate (EC). But, the freezing point of EC-based electrolyte increased due to the high freezing point of . Therefore, EC+PC mixed electrolyte is expected as a good organic electrolyte for lithium ion battery. The EC-based organic electrolyte containing PC within pertinent quantity can be expected to have high molar conductivity and reduced exfoliation of graphite layer. The dielectric constant and molar conductivity of electrolyte was investigated with a variation in the PC content. The electrochemical properties of carbon electrode in the electrolyte were also investigated. Molar conductivity and dielectric constant increased linearly by increasing the PC volume fraction in the electrolyte. The results of charge-discharge test for carbon/electrolyte/Li cell indicated that the initial irreversible specific capacity(IIC) of MCMB-6-28s and MPCF3000 decreased by the addition of of PC, but increased with PC content over than . In the case of MPCF3000 and PCG100 having less than PC, IIC was lower than 50 mAh/g. The discharge specific capacities varied with carbon material, but did not vary with PC content in the electrolyte.